Coils Optimisation to Avoid Parasitic Capacitance Effects in an Inductive Wireless Charger for Underwater Vehicles

The integration of inductive charging technology in electric vehicles has aroused the interest of researchers in recent years. Specifically, one of the growing areas is wireless charging in Autonomous Underwater Vehicles (AUVs). In this environment, the effects of seawater in wireless power transmission should be carefully studied. Specifically, one of the effects that should be analysed is the appearance of parasitic capacitances (Ce) between the power coils due to the high conductivity of seawater. The parasitic capacitance, together with the power converters switching losses and the resistive and inductive losses, can lead to a drop in efficiency during the charging process. The main objective of this contribution is to find the optimal solution to avoid the effects of Ce during the coils design, thus simplifying the process and making it equivalent to an air-based solution. To do so, different design criteria have been defined with a comparative analysis among different topologies proposed. Specifically, we have studied the variations of voltage, current, and efficiency caused by the Ce. Additionally, a comparison between Series-Series (SS) and LCC–Series (LCC–S) compensation systems has been considered, studying the system efficiency and maximum current values found on the circuit. The results of these studies have been verified through experimental validations, where the design and implementation of the elements that constitute the inductive charger have been performed. This validation has demonstrated the possibility of neglecting the effects of Ce by optimising the coil’s design.